Fiber-optic angle sensor based on an extrinsic Fabry–Perot cavity

The purpose of this study has been devoted to the presentation and demonstration of an extrinsic Fabry–Perot cavity (EFPC) fiber-optic angle sensor, which consists of a cam, linear displacement attenuators, and an EFPC. An angle can be transformed into a linear displacement that is subsequently attenuated by linear displacement attenuators to modulate the EFPC when the cam is driven to rotate by a rotary object, which causes the output intensity of EFPC to vary. In order to fully demonstrate the advantages of EFPC, based on the multi-period characteristics of EFPC output and cam rotation, it is shown that an infinite angle can be measured accurately and continuously by counting the number of fringes whereas a small angle can be measured in a locally linear region of response function of EFPC.